Anticipated Impacts on Veterans Healthcare: This research will inform provider- and system-level interventions to optimize the effectiveness of evidence-based psychotherapies (EBPs) for Posttraumatic Stress Disorder (PTSD) in routine clinical practice. Project Background: VHA has committed considerable resources to ensuring that all veterans with PTSD have access to EBPs. These efforts have focused primarily on two EBPs for PTSD ? Cognitive Processing Therapy (CPT) and Prolonged Exposure (PE). Over the past decade more than 6,300 VHA clinicians have received VHA competency based training in CPT or PE. Therapists providing CPT and PE are required to use templated CPT and PE chart notes for session documentation, providing detailed information on the prescribed elements of CPT and PE delivered in each session. Prior research on CPT and PE has focused primarily on treatment outcomes, uptake among providers and reasons for drop-out among patients. Understudied are systematic differences between therapists in their effectiveness, indicators of the quality of CPT and PE delivery, and the work conditions conducive to positive outcomes. By addressing these evidence-gaps, we will identify modifiable factors affecting CPT and PE delivery that we can target for intervention and thereby improve treatment retention and clinical outcomes among Veterans with PTSD. Project Objectives: Specific aims are to: (a) Examine systematic differences between therapists in CPT and PE outcomes, and whether certain therapists are more effective with vulnerable patient subgroups, and (b) Determine whether the therapeutic relationship and therapist adherence predict CPT and PE outcomes and whether these indicators of therapy quality explain systematic differences between therapists in patient outcomes. Exploratory aims are to: (a) Determine whether the intensity and consistency of time between sessions contribute to patient outcomes and at least partially account for systematic differences between therapists in patient outcomes; (b) Examine whether therapist caseload, clinic setting and resources for therapy delivery in therapists' work environment contribute to patient outcomes and at least partially account for systematic differences between therapists in patient outcomes; and (c) Elucidate quantitative findings on therapist effects, therapy quality and aspects of therapist work context associated with patient outcomes through qualitative interviews. Project Methods: This is an explanatory sequential mixed-method study of 200 therapists who deliver CPT or PE to approximately 2,000 patients with PTSD. Therapists will be enrolled if they use the chart note templates VHA requires for documentation of CPT and PE and treat at least three patients with CPT or PE over one year. Patients of these therapists will be included if they have a diagnosis of PTSD and receive at least two sessions of CPT or PE. After enrollment, therapists will complete a brief online CPT and PE template refresher tutorial to ensure high quality CPT and PE documentation and a survey to assess training history and resources for EBPs in their work environment. Patient retention in treatment and clinical improvement in PTSD are the primary outcomes. To partition the total variance in patient outcomes between patient and therapist levels, we will use multilevel modeling of therapist and patient data from VHA administrative datasets and chart notes, supplemented with survey data. Qualitative interviews with a purposive sample of 32 therapists after quantitative data collection will contextualize, explain and illustrate quantitative findings. 1